So, kazeshini is best pvp zanpakuto for f2p, tengen is good when u want make your vangu harder to kill but its cost u speed and dmg for supports and assualters.
Zanpakuto for f2p:
pvp-best kazeshini if u want to have speed and dmg at assualters and supports or tengen if u like to have strong vangu. Im still using kazeshini at 100+lvl like rest f2p/low vip lvl ppl.
pve= zabimaru, if u dont have him use kazeshini until u get zabi.